The dealer I bought my FZ6 from, said a 600 mile service was not needed. He just said be sure and change the oil and filter. I like dealers like that...
How do you know this (that warranty is voided)? Something's wrong, paying 120 Euros for something that shouldn't be over 10 Euros. Have you considered writing a complaint to Yamaha?
According to the service manual from what I read it is voided. Its in Greek so maybe this is the policy of Yamaha Greece. As for the price, it is not considered that is was too expensive for Greek standards. It was but not alot. But from what most of you guys pay it is....
Mine was about $125 for the 600 mile service. Oil, fliter and FI sync sticks. Now that I know how to sync the FI my future costs will be parts and fluids only, until I get to the valve asjustment at 24K.